1. Technical Field
The present invention relates to an ophthalmologic apparatus and an image classification method, and more specifically to an ophthalmologic apparatus and an image classification method for quantitatively measuring abnormalities in the quantity and quality of tear film and classifying types of dry eye.
2. Background Art
In recent years, the number of patients with dry eye has increased due to an increase in the number of visual display terminal (VDT) workers, drying of rooms by air-conditioning, and the like. There is a risk that disorders in the corneal epithelium, conjunctival disorders, and various other ophthalmic disorders may occur in conjunction with dry eye, and the diagnosis of dry eye has become an important subject of ophthalmologic diagnosis.
Diagnosis of dry eye has been conventionally performed by vital staining test, a test of the amount of tear fluid secretion by Schirmer's test, and the like. However, there are problems in reproducibility of test results and objectivity because of the involvement of chemical eye drops and contact with foreign objects with the result of unavoidable pain for the examinee.
In order to diagnose dry eye without contact, the change with time of a dry spot region generated from the break up of the tear film after opening the eyelid of the eye to be examined is measured as a change with time in area ratio data of the dry spot region, and the change with time in the dry spot region is displayed on a monitor to check abnormalities in the stability of tear film in dry eyes (Patent Document 1).
Furthermore, in order to quantitatively evaluate abnormality in the tear fluid in the dry eye, diagnosis of dry eye is also performed by measuring the intensity of an interference pattern due to interference of reflected light on the obverse and reverse surfaces of the tear film lipid layer and calculating a value showing an abnormality in the tear film in the dry eye from the measured value (Patent Document 2), or setting a plurality of areas in the image of the interference pattern and evaluating the tear film surface layer on the basis of the hue of each area (Japanese Patent 3), or analyzing the change of the hue of interference fringes with time (Patent Document 4). Diagnosis of abnormality in the tear film in the dry eye is also performed by imaging the tear film lipid layer on the cornea and calculating the movement speed of the tear film lipid layer at the time the eyelid is opened (Patent Document 5).
Additionally, the tear film is observed without staining with fluorescein, and the time until the tear film is broken up and forms a dark-area (DARK-AREA), i.e., non-invasive break up time (NIBUT) is measured to evaluate abnormality in the tear film in the dry eye (Non-Patent Document 1).